Pneumatic reverse acting relay



Nov. 18, 1952 c. M. JOHNSON 2,618,286

' PNEUMATIC REVERSE ACTING RELAY Filed Aug. 1'7, 1948 3 Sheets-Sheet l l d w l|m|H*' IN INVENTOR. N dead/111227150. s

yad 7 204 4 Nov. 18, 1952 c. M. JOHNSON 2,618,286

PNEUMATIC REVERSE ACTING RELAY Filed Aug. 17, 1948 s Sheets-Sheet 2 00 96) H .104 I T Jaye/1227:- 6017 M Jansm V flzm/yam ligys.

Nov. 18, 1952 c. M. JOHNSON 2,618,286

PNEUMATIC REVERSE ACTING RELAY ]N VEN TOR.

Patented Nov. 18, 1952 UNITED STATES PATENT orncs iron-aims. 1

This invention relates to pneumatic reversing relays also "known as reverse acting relays, and particularly to'such a relay which delivers a pressurathatwaries inverselyas the instrument or control pressureun a valve operator .or the like utilizing a pneumatic diaphragm motor.

An example oi. suchv a motor and motor and relay combination is described and claimed in the copending application of Donald 'J. Gafiney', Serial No. "44,780,. .file'd; August '17;- 21948, now Patent No. 2,601,511,,iorPneumatically Operated Diaphragmilvlfotors. 'Insuch a, system, the.relay operates sothat .as the control. air pressure increases, 'the delivery pressure fr'omuthesrelay decreases in. the sameproportion and vice-versa. This application relates to the relays per se.

'It'is an object of itheinven'tion.toprovide come pactand reliable reversing relays .of 'the- .pneuma'ti'c type which deliver output pressures inversely proportional. to control pressures.

It 'istano'ther object of the I invention to provide pneumatic reversing relays (which ar readily adjustable.

'Itis also an object ofthefi'nvention to .providedevice whereby the objects contemplated are.

attained, as hereinafter more fully set forth, pointed out in the claims and illustrated (in lthe accompanying; drawings, wherein:

.Figure 'lfi's an elevational'v'iew, partially in section; illustrating. one embodiment of .a reversing relay applied "to a double diaphragm pneumaticrmctor, "including a .positioner, .for moving the stem of a valve or governor;

Figure 2"is a sectional view of .a bellows'and valve assembly *operatedfby the positioner;

Figure 2a is an enlarged sectional view of the relay shown in Figure '1;

Figure.3 is a sectional .view ofthe relay taken oniline'3 3 of Figure T1;

"Figure 4 is a verticalsectional viewofa reversingrelayconstructed'in accordance with aisecond' embodiment of theinvention;

Figure 5 is a vertical sectional .view'taken on line 5-5'0'1? Figures; and

Figure 6 is "a horizontal sectional view taken on line 6 6 o'f'F'igure Referring speci'fically tothe drawings, particularly Figures "1 and '2, fora detailed description of thefirst'embodiment "of "the invention, .a valve body' is indicated generally at 2| and may be 12 any conventional control valve, butterfly valve; turbine "governor control, 'orthe like, well-known in the art. A mechanism for operating the valve" or governor includes a-double'diaphragm asse1nbly generally in'd'i'catedat 22,"operating a'rreciprm eating stem 23, a conventional'va'lve positioriei" 24 and a reversing :relay 2'6, 'all heingwonnecte'd to each other and to the 'doublediaphragm assembly by jsuit'ablejpiping tobe "described.

The "double "diaphragm assemblyzlcomprises an upper cup-shaped icasin'gmember 2-1.2; lower cup-shaped casing member-2a and an intermediate annular or =ring'shaped meni'ben'ZQ; upper diaphragm, formed of rubber' or' synthetic rubberlikem'aterial. is clamped between the easing members-21 and"29', anda 'lower'rnhher '01? synthetic rubber diaphragm isclamped between the casing members .ZB' and "2'9. Bolts "(not shown "are provided for retaining "the' casing members together.

Th va-lv'estem '23 is *provided'with ran-enlarged portion 33, which is dispos'eiti'vtiiiiirii'ritl'reflotiblci diaphragm *member 2 2. The enlarged portion of stem 23 engages with'ajplate 3-4--disposed 'cn Apnea-as engages'with'the upper-surfaceof the diaphragm Hand is clamped to-the-pl'atefll with "the dia phragm 3'! therebe'tween by "a :nut 36'.

A plate 31' *is disposed beneath theemargied portion 33 in contact with the upper surfz'i'ceinf the diaphragm '32. Apla'te "38 elampsithe diaphragm '32 between itse'lf rand theyplate filthy means or a"nut'139secured to stem 23. Movement "of either'niaphragm is, therefore, trans;

*m'itted to the other without :slaick': Atmospheric pressure .is ,present "betweentlie diaphra m; and 32.

The stem 23 extends through itheTlowercasing member 28 and" into the casing It, .a packing gland illbe'ing provided "in thel'ower vcasing portion Z8'for the stem 23.

The diaphragms 3i and '32 divide. the doulcile diaphragm 22 into an. upper chamber 4'1, atmwer chamber -42' and an" "intermediate".chan'iber 1'3; A'eonduit or pipe Mcommunica'teswith the upper:

cham'b'er tl; and a conduit (45' communicates-wi h the :lower chamber, fora purpose hereinafter described.

A'va'lve positioner plate 148 supportsilevers I1} 48 and "49. 'The'lever l'l'is pivotallynonneetetl to valve stem .23 at "50. Thejlevers I4! anal-I8" are connected together and are pivotally .supported onthe plate "46 'at 52'. The lever 49 is pivotally connected to Ztheipl'ate 46 atiilizandmis providedwith alongitudi'nal slot 52a. 'The'lever 3 49 is also pivotally connected to a block 53 which slides in slot 52a, so that vertical movement of stem 23 rotates lever 99 about its pivot 5|. A threaded member 55 is pivotally connected to the lever 49 at 54 and has a threaded abutment member 56 thereon which engages with a. spring 51, and is adjustable to vary the compression thereof. r

A combination bellows and valve member, generally indicated at 69, comprises a main body portion 58, having an open ended casing 59 secured to one side thereof adjacent spring 51, and a closed cup-shaped member 8| secured to the other side thereof. A bellows 82 is secured to the side of the main body portion 58 facing the spring 51, and a bellows 63 is secured to the other side of the main body portion 58 and is contained within the casing 6|. Rods 69 extend through openings 83 in the body portion 58 and engage a plate 98 secured to bellows 63, and plate 61 secured to bellows 92. spring 51 also engages the outside of plate 61 and tends to collapse bellows Theplate 81 is provided with a central opening 68 therein, which provides a seat for a valve member 6 9,"which is a part of a valve assembly 1|, which in turn has a second valve member 12 on it s inner extremity. A spring 19 engages the inner valve member 12, and the plate 81 tends to maintain the valve member 12 seated on its seat 19 formed in body member 58. A pair of passages 'I' liand 15 are also provided in body member 58 incomm-unication with a conduit 18. The valve member '12 operates to'open and close passages 14land 15, which communicate with conduit 16, me. manner hereinafter described. A conduit 11, which communicates with a standard instrument or. controller (not shown), also communicates witha-passage 18- in body 58, which passage 18 opens into a chamber 19 formed between casing member Bland bellows 63. Casing 19 is, obviouslyfh'ermetically sealed.

{Anothe'r conduit 8|, which communicates with conduit'ABT-and lower chamber 42 of the double diaphragm member 22, also communicates with ai pas'sage 82 in body 58, which in turn communicai'feswith passages 83 in body 58 through which rod's'fi l extend. Conduit BI is, therefore, in communication with the interior of the bellows 62 atidfiill' reversing relay 26 comprises a central body portion 84, towhich is secured an upper body portion 85 and'a lower body portion 89. A chamberfilli'is formed in the central body portion 89 of; reversing. relay 26, and a conduit 98 communicates withjth'e chamber 81 to a bore 89 at one end thereof and with conduits 95 and BI at the otherend thereof. I

;-A'diaphragm 9| formed of rubber or synthetic rubber is clamped between the upper portion 85 and the central portion 84 of the relay, and the diaphragm 92 is clamped between the lower portion 86 and the central portion 84 of the relay. Bolts may be utilized for retaining the parts together. The eiiective area of the lower diaphragm 92 is approximately twice that of the upper diaphragm 9|. A stem 93 is secured to the upper,

and lower diaphragms SI and 92, in any suitable manner, the stem 93 being provided with a central passage 94 extending therethrough. A valve assembly 99 has an upper valve member 95 and a lower'valve member 96. The lower valve member 96 normally closes the upper end of passage 94; The upper" body portion 85 of relay 26 is provided with a boss 91, which is internally screw threaded to receive a plug 99. A spring 99 engages with the plug 98 and with the upper valve member 95 to normally bias the valve member 95 into engagement with its seat |9| surrounding a passage I99 in body portion 85. The spring 99 also biases the valve member 96 into engagement with its seat I 92 on top of stem 99.

A passage I93 is provided in the upper body portion of relay 25, and communicates at one end with pipe 99, which in turn is in communication with upper chamber 4| of the double diaphragm member 22. The other end of passage I93 communicates with a chamber I94, which is formed above diaphragm 9|. A second passage I is provided in the upper body portion 85 of relay 26, which communicates at one end with a conduit I98 and at its other end with a chamber II9 above valve member 95. The conduit I96 also communicates with conduit 19 and with a conduit I91, which latter conduit connects with a regulated air supply.

The lower body portion 86 is provided with an internally threaded boss I99, into which is screwed a hollow plug III having a vent H2 in the side thereof. A spring I I3 engages the closed end of the plug I I I and engages with a plate II4, which is secured to diaphragm 92, thus tending to bias stem 93 upwardly into engagement with valve member 96.

Operation of Figures 1 and 2 Referring first to the reversing relay 26, assuming a 20 p. s. 1. air supply through conduit I96, then with no pressure at conduit 8|, adjusting screw or plug III is screwed down to adjust the spring ||3 until the diaphragm or delivery pressure in conduit 94 is 20 p. s. i. The efiective area of diaphragm 92 is twice that of diaphragm 9|, as stated hereinbefore. If the area of diaphragm 9| is equalto y, the area of diaphragm 92 is equal to 2y. If theinstrument or control pressure at 8| is increased 1 p. s. i., there will be an increase in force on diaphragm 92 equal to 22/ and an increase in force on diaphragm 9| equal to y. This leaves a net unbalanced downward force on the diaphragm assembly equal to y and, consequently, the assembly Will move, opening the bleed valve 96. This will allow air to escape from the chamber I94 until the pressure on the top of diaphragm 9| is reduced 1 p. s. i. The diaphragm assembly will again be in static balance, and the bleed valve 96 closed. Thus, it becomes apparent that with every pound increase at 8|, one pound decrease will resultat 44., v v

If there is a 1 p. s. 1. decrease at 8|, this will result in a 1 p. s. 1. increase at 44, because the diaphragm assembly of the relay 26 will move upwardly, opening inlet valve 95 and permitting increase in pressure in chamber I99 and in conduit 94 until the pressures are again balanced, whereupon the inlet valve 95 is closed.

Referring now to the complete air circuit, starting with the air from the instrument, or controller which enters through conduit 11, increasing air pressure will cause the bellows assembly 62, 63 to be moved to the left as viewed in Figure 2, which opens theair supply valve 12 allowing air supply pressure entering through conduits I91 and 16 to flow into the chamber formed by the two bellows 92, 63 and through conduit 8| into lower diaphragm chamber 42 of the mo- I tor valve 22. The same increase in pressure is also registered in chamber 81 of reversing relay 26 which, as explained above, causes an.unbalance in the relay diaphragm assembly and causes ears-see it to move downwardly allowingair to escape mm chamber I04 through passage 94 and bleed outlet I-I 2. This lowers the pressure in the chamber of the motor 22 in an amount equivalent to the rise in pressure in the chamber 42 of motor 22. There is now an unbalanced force on the main diaphragm assembly 3|, 32, which causes the valve stem 23 to move upwardly. This supplies compression to the spring 51 through the levers 41, 48 and 49, which balances the increase in pressure on bellows assembly 62, 63, causing supply valve I2 to again close. This places the system again in balance. If, due to hysteresis in the diaphragm assembly 3I, 32, sticking in the stufiing box 40 or unbalanced pressure "forces on the valve or governor being operated; the valve stem 23 does not move immediately, air will continue to bleed through the inlet valve 72', consequently increasing air pressure-in the-chamber and decreasing pressure in the cham-ber 4| until the valvestem 23 moves or until the pressure in chamber 42 has increased to the equivalent of the air supply, that is 20 p. s. i., and the air pressure in chamber 4| has reached-zero. This makes available fo moving the valvestem 23 a force equivalent to the product of the diaphragm area 32, times the supply pressure. For example, if the diaphragm area is 100 square inches and the air supply is 20 p. s. i., there is 2000 p. s. i. force available to move the valve stem 23.

O'n decreasing pressure from the instrument or controller through conduit 11, the bellows assembly 62, 63 will move to the right as viewed in Figure 2. Since the inlet port I2 is closed, the inner valve II cannot move further to the right. Consequently, the left hand bellows head 51 breaks away from bleed valve 63, opening the bleed port 68 and allowing air to bleed from the chamber formed by the bellows 62, 53. This decreases the pressure in chamber 81 of reversing valve 26 and in chamber 42 of the motor 22. The decrease in pressure in chamber 81 causes an'increase in pressure in chamber 4| of motor 22', as explained above. The unbalance on the diaphragm assembly 3|, 32 will now cause the valve stem 23 to move downwardly, which through levers M, 48 and 49, will decrease the loading on spring 51 until the spring load again balances the pressure load from the instrument or controller in the chamber formed by bellows 63 and cup shaped'member 6|, thus closing bleed valve 59 and placing the system again in balance.

Description of Figures 4, 5 and 6 Referring now to Figures 4, 5 and 6 for a detailed description of the reversing relay constituting the second embodiment of the invention, the principle is the same as that referred to with respect to Figures 1 and 2, although the force balance is slightly different. The reversing relay shown in Figures 4, 5 and 6 is intended to be used in the same system as shown in Figures 1 and 2, that is, with a pneumatic motor 22, a stem'23, a valve or governor 2|, a positioner 24 and a bellows 'valve assembly 60. In the embodiment shown in Figures 4, 5 and 6, the reversing relay as shown in Figure 1 has been inverted, since the relay is capable of operating in any'position and may have its outlet connected either to the upper chamber 4| of motor 22 or to the lower chamber 42 of motor 22, depending upon the desired direction of operation of the valve-stern 23.

In the construction shown in Figures '4, 5 and 6, numeral I2I designates the main portion or the relay body, I22 an upper casing portion-se cured to the body I 2I and numeral I23 a lower casing portion secured to body I-2I-. A diaphragm I24, formed of rubber or synthetic rub her, is clamped between the members I21 and- I22, and a similar diaphragm I25 clamped between members I 2'I and I23. The upper diap'hragm I24 has an eife'ctive area twice that of lower diaphragm 125. A chamberflfi is formed above the upper diaphragm I24, and a chamber I2! is formed below the upper diaphragm I24. A chamber I28 is formed below the lower diaphragm I25. A chamber I 29 is formed in the body I2I and has a coil spring I3I positioned therein. A plug I30 closes the chamber I29 and has a passage I20 therethrou'gh providing a seat for a lower valve member I3! of a valve I32. The valve I32 has an upper valve member I33 provided with a seat I34 in ahollow stem member I35 having a passage I36 therethrough.

A pair of rods I39 extend through vertical passages I40 in the body I2I and are'riveted at their lower ends to a pair of plates I4I, which clamp the diaphragm I25 therebetween. The rods I39 are riveted at their upper ends to a plate I42, which is secured to the stem I35 and clamps the diaphragm I24 thereto.-

The upper casing portion I22 is provided with an internally threaded bo-ss I44,- into which is screwed a hollow plug I45 having a vent. opening I45 therein. Theplug I45 has a spring I4! therein, which is in contact with the top of the plug I45 and with the plate I42, thus tending to force the hollow stem member I35 and the diaphragm I23 downward. This maintains the valve I33 normally seated on seat I34, but the force of the spring I41 is not normally sufiicient to unseat valve member I3I from its seat I33 against the force of spring I3I and the unbalanced force resulting from air pressure on diaphragm I24 and I25.

An internally threaded passage I48 connects with the chamber I29 in body I2I and is'adapted to be connected to the air supply pressure conduit IQ; of Figure 1. An internally threaded passage Me communicates with chamber I21 in the body 12E and is adapted to be connected either to chamber 4i or chamber 42 of motor 22 in Figure 1, depending upon the direction of operation of stem 23 desired. An internally threaded passage I52 is provided in boss I5I of lower casing member I23 and communicates with chamber I28. The passage I52 is adapted to be connected to the instrument or control pressure through conduits SI, 88 of Figural.

Operation of Figures 4, 5 and 6 As stated above, the area of diaphragm I24 is twice that of diaphragm I25. If the area of diaphragm I25 is equal to y, the area of diaphragm I24 is equal to 2y. With 20 p. s. i. air supply in passage I58 and chamber I25, the adjusting screw or plug I45 is set so that there is 20 p. s. i. in chamber I21 and, therefore, the same pressure in passage I49, which is connected to motor 22 with no pressure in passage I52, or

chamber I25, which is connected to the instrument or control. If the instrument or control pressure is increased in passage I 52 and chamber I28 to 1 p. s. i., there will be an increase in the upward force of diaphragm I25 equal to y. This will cause the diaphragm assembly to move up- 'wardly to separate valve member I 33 from its bleed until the pressure has been reduced one pound in chamber I2'I. When this has occurred, the upward force in diaphragm I24 will have been decreased to 2y and the downward 'force on diaphragm I25 will have been decreased y. The net result of the change in pressure in chamber I21 will be a-decrease in upward force equal to y. This decrease will be replaced by 1 p. s. i. increase in passage I52 and chamber I28, which will close valve member I23, and the relay will again be in equilibrium. Thus, an increase of 1 p. s.- i. in passage I52 and chamber I28 causes a decrease of 1 p. s. i. in chamber I2! and passage M9.

'In the reverse cycle, a decrease in pressure in passage I52 and chamber I28 will cause a like increase'in chamber I 21 and passage I49, because the diaphragm assembly I24, I25 moves downwardly, opening valve member I31 against the force of spring I3I and efiecting an increase in pressure in chambers I27 and I49 until equilibrium is again reached, whereupon valve member $31 will be seated on its seat I38.

From the foregoing, it will be apparent that I have provided an improved pneumatic reversing relay which is capable of wide range application.

Some changes may be made in the construction and arrangement of the parts of my device without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may be reasonably included within their scope without sacrificing any of the advantages thereof.

I claim as my invention:

1. A pneumatic reverse acting relay comprising a first chamber communicating with a supply of pressure fluid, a. port in said first chamber, a valve member having a first Valve for opening and closing said port, means for normally biasing said first valve to closed position, a second chamber into which said port opens for admitting pressure fluid thereto, a passage for fluid communicating with said second chamber, one wall of said second chamber comprising a first flexible diaphragm, a movable member secured to said first diaphragm and having a passageway therethrough, said valve member including a second valve for opening and closing said passageway, said passageway communicating with said second chamber at one end thereof when said second valve is open and with atmosphere at the other end thereof, means for normally retaining said second valve in closed position, and a third chamber having an opening therein for fluid under pressure, two walls of said third chamber being formed by said first diaphragm and a second diaphragm, said second diaphragm also being secured to said movable member.

2. A pneumatic reverse acting relay comprising a first chamber communicating with a supply of pressure fiuid, a port in said first chamber, a valve member having a first valve for opening and closing said port, means for normally biasing said first valve to closed position, a second chamber into which said port opens for admitting pressure fluid thereto, a passage for fluid communicating with said second chamber, one wall of said second chamber comprising a first flexible diaphragm, a movable member secured to said first diaphragm and having a passageway therethrough, said valve member including a second valve for opening and closing said passageway, said passageway communicating with said second chamber at one end thereof when said second valve is open and with atmosphere at the other end thereof, means for normally retaining said second valve in closed position, and a third chamber having an opening therein for fluid under pressure, two walls of said third chamber being formed by said first diaphragm and a second diaphragm, said second diaphragm also being secured to said movable member, one of said diaphragms having a larger effective area than the other.

3. A pneumatic reverse acting relay comprising a first chamber communicating with a supply of pressure fluid, a port in said first chamber, a valve member having a first valve for opening and closing said port, means for normally biasing said first valve to closed position, a second chamber into which said port opens for admitting pressure fluid thereto, a passage for fluid communicating with said second chamber, one wall of said second chamber comprising a first flexible diaphragm, a movable member secured to said first diaphragm and having a passageway therethrough, said valve member including a second valve for opening and closing said passageway, said passageway communicating with said second chamber at one end thereof when said second valve is open and with atmosphereat the other end thereof, means for normally retaining said second valve in closed position, and a third chamber having an opening therein for fluid under pressure, two walls of said third chamber being formed by said first diaphragm and a second diaphragm, said second diaphragm also being secured to said movable member, one of said diaphragms having an efiective area approximately twice that of the other.

4. A pneumatic reverse acting relay comprising a first chamber communicating with a supply of pressure fluid, a port in said first chamber, a valve member having a first valve for opening and closing said port, means for normally biasing said first valve to closed position, a second chamber into which said port opens for admitting pressure fluid thereto, a passage for fluid communicating with said second chamber, one wall of said second chamber comprising a first flexible diaphragm, a movable member secured to said first diaphragm and having a passageway therethrough, said first valve member including a second valve for opening and closing said passage-s way, said passageway communicating with said second chamber at one end thereof when said second valve is open and with atmosphere at the other end thereof, means for normally retaining said second valve in closed position, and a third chamber having an opening therein for fluid under pressure, two walls of said third chamber being formed by said first diaphragm and a second diaphragm.

5. A pneumatic reverse acting relay comprising a first chamber communicating with a supply of pressure fluid, a port in said first chamber, a valve member having a first valve for opening and closing said port, means for normally biasing said first valve to closed position, a second chamber into which said port opens for admitting pressure fluid thereto, a passage for fluid communicating with said second chamber, one wall of said second chamber comprising a first flexible diaphragm, a movable member secured to said first diaphragm and having a passageway therethrough, said valve member including a second valve for opening and closing said passageway, said passageway communicating with said second chamber at one end thereof when said second valve is open and with atmosphere at the other end thereof, means for normally retaining said second valve in closed position, a third chamber having an opening therein for finid under pressure, two walls of said third chamber being formed by said first diaphragm and a second diaphragm, said second diaphragm also being secured to said movable member,spring means for biasing said diaphragms one direction, and means for adjusting the bias produced by said spring means.

6. A pneumatic reverse acting relay comprising a casing, first, second, and third chambers in said casing, first, second, and third passages in said casing respectively in communication with said chambers, a first connecting passageway between the first and second chambers, a movable member having a second connecting passageway therethrough communicating at one end with said second chamber and at the other end with atmosphere, a valve member having a first valve for opening and closing said first connecting passageway, said valve member having a second valve for opening and closing said second connecting passageway, a first diaphragm between the second and third chambers, a second diaphragm bounding one of said latter two chambers, said diaphragms being rigidly connected together to move as a unit, said movable member being secured to at least one of said diaphragms, and said first diaphragm being of smaller area than said second diaphragm, whereby a change of pressure in said third chamber causes one of said valves to be opened to cause a reverse change in pressure in the second chamber.

'7. A pneumatic reverse acting relay as set forth in claim 6 wherein said second diaphragm has an effective area approximately twice that of the first diaphragm.

8. A reverse acting relay as set forth in claim 6 including spring means for biasing said diaphragms in one direction, and means for adjusting the bias produced by said spring means.

9. A pneumatic reverse acting relay comprising a casing, first, second, and third chambers in said casing, first, second, and third passages in said casing respectively in communication with said chambers, a first connecting passageway between the first and second chambers, a movable member having a second connecting passageway therethrough communicating at one end with said second chamber and at the other end with atmosphere, a valve member having a first valve for opening and closing said first connecting passageway, said valve member having a second valve for opening and closing said second connecting passageway, a first diaphragm between the second and third chambers, a second diaphragm bounding one of said latter two chambers, said diaphragms being rigidly connected to gether to move as a unit. said movable member being secured to at least one of said diaphragms, said first diaphragm being of smaller area than said second diaphragm, whereby a change of pressure in said third chamber causes one of said valves to be opened to cause a reverse change in pressure in the second chamber, said diaphragms and movable member having a balanced position wherein both valves are closed, the displacement from said balanced position of said diaphragms and movable member in one direction affording opening of said second valve, and the displacement from said balanced position of said diaphragms and movable member in the other direction affording closing of said second valve and opening of said first valve.

10. A pneumatic reverse acting relay comprising a casing, first, second, and third chambers in said casing, first, second, and third passages in said casing respectively in communication with said chambers, a first connecting passageway between the first and second chambers, a movable member having a second connecting passageway therethrough communicating at one end with said second chamber and at the other end with atmosphere, a valve member having a first valve for opening and closing said first connecting passageway, said valve member having a second valve for opening and closin said second connecting passageway, a first diaphragm between the second and third chambers, a second diaphragm bounding one of said latter two chambers, said diaphragms being rigidly connected together to move as a unit, said movable member being secured to at least one of said diaphragms, means for normally biasing said first valve to a closed po ition, means for normally retaining said movab e member against said second valve to close said second connecting passageway and said first diaphragm being of smaller area than said second diaphragm, whereby a change of pressure in said third chamber causes one of said valves to be opened to cause a reverse change in pressure in the second chamber.

11. A pneumatic reverse acting relay comprising a casing, first, second, and third chambers in said casing, first, second, and third passages in said casing respectively in communication with said chambers and adapted for connection to sources of fluid under pressure located exteriorly of said casing, a first connecting passageway between the first and second chambers, a movable member having a second connecting passageway therethrough communicating at one end with said second chamber and at the other end with atmosphere, a valve member having a first valve for opening and closing said first connecting passageway, said valve member having a second valve for opening and closing said second connecting passageway, a first diaphragm between the second and third chambers, a second diaphragm bounding one of said latter two chambers, said diaphragms being rigidly connected together to move as a unit, and said movable member being secured to at least one of said diaphragms.

12. A pneumatic reverse acting relay as set forth in claim 11 wherein said second diaphragm serves as one of the walls of the third chamber.

13. A pneumatic reverse acting relay as set forth in claim 11 wherein said movable member is secured to said second diaphragm.

14. A pneumatic reverse acting relay comprising a casing, first, second, and third chambers in said. casing, first, second, and third passages in said casing respectively in communication with said chambers and adapted for connection to sources of fluid under pressure located exteriorly of said casing, a first connecting passageway between the first and second chambers, a movable member having a second connecting passageway therethrough communicating at one end with said second chamber and at the other end with atmosphere, a valve member having a first valve for opening and closing said first connecting passageway, said valve member having a second valve for openingand closing sa'idsecond connecting passageway, a first diaphragm'between the second and third chambers, two of the walls of said second chamber comprising said first diaphragm and a second diaphragm, said diaphragms being rigidly connected together to move as a unit, and said movable member being secured to said first diaphragm.

15. A reverse acting relay as set forth in claim 14 wherein one of said diaphragms has a larger effective area than the other.

16. A reverse acting relay as set. forth in claim 14 wherein one of said diaphragms has an effective area approximately twice that of the other.

17. A reverse acting relay as set forth in claim 14 including spring means biasing said dia- 12 phragms in one direction, and means for adjusting the bias produced by said spring means.

CECIL M. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Edwards Oct. 27, 1942 

